been summoned2court as a witness

[t1000]

hi,ive been summoned 2 go to court as a witness to a gbh (possibly with intent) and the police want me to go against my close friend whom is in introuble 4it...i ve alrdy given a statement but am not willing 2 go 2 court and get a m8 slammed,hes gonna get locked up anyway so im stil questioning why im needed 2attend....my question 2day is IF i didnt turn up to the court case, what is most likely goinog 2 happen to me??
i also have2 go court myself ina few months for a domestic abuse case...do u think if i missed the first case wud it end up effecting the 2nd one (even tho they arent related)? and wot r the possible outcomes for me?